The U.S. Supreme Court Tuesday refused to order immediate closure of shipping locks near Chicago to prevent Asian carp from infesting the Great Lakes. According to the Associated Press, the court rejected a request by Michigan for a preliminary injunction to close the locks temporarily while a long-term solution is sought to the threatened invasion by the exotic fish. The one-sentence ruling didn't explain the court's reasoning.

Michigan, joined by Minnesota, New York, Ohio and Wisconsin and Ontario, asked the high court to order the locks closed as a stopgap measure while considering a permanent separation between Lake Michigan and the Mississippi River basin. The state of Illinois, backed by the Obama administration, fought the proposal arguing there wasn’t sufficient evidence carp were on the verge of slipping into Lake Michigan, and said closing the locks would damage shipping and passenger traffic on the busy waterway.

Asian carp have been migrating up the Mississippi and Illinois rivers toward the Great Lakes for decades. They have swarmed waterways near Chicago leading to Lake Michigan. Scientists fear that if they reach the lakes, they could disrupt the food chain and endanger the $7 billion fishery.

Last week, the U.S. Army Corps of Engineers said additional carp DNA — but no live fish — had been found in three different spots along the Chicago River within a mile of where it flows into Lake Michigan.